Heating effect of Current and Joule’s Law of Heating

When an electric current is passed through a conductor, heat is generated. This effect is called heating effect of current. This effect was introduced by Joule. So, it this effect is also called Joule’s law of heating. Electric devices like electric iron, heater, fan works on the principle of Joule’s law of heating.

According to Joule’s law of heating, the amount of heat produced in a conductor is directly proportional to:

  1. Square of current (H∝I2)
  2. Resistance of the conductor (H∝R)
  3. Time upto which current is passed (H∝T)

Combining these relations, we get:


H=kI2RT  (where ‘k’ is proportionality constant)

In SI unit, k=1

∴ H=I2RT Joule

But, In C.G.S system, $\text{K} =  \frac{1}{\text{J}}$

Here, J=Joule’s mechanical equivalent of heat.

$\text{So, H} =  \frac{\text{I}^2\text{RT}}{\text{J}}\text{Cal}$

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